JS面向对象的私有属性 set 和 get

function User(name,password,phonenumber){
      var phonenumber=phonenumber
      this.name=name
      this.password=password
      //建立私有属性的访问方法
      this.getphonenumber=function(){
           return phonenumber
      }
      //建立私有属性的设置方法
      this.setphonenumber=function(number){
           var reg=/\d{11}$/
           if(reg.test(number)){
                phonenumber=number
           }else{
                alert("格式不正确")
           }  
       }
}

var u1=new User("admin",213,15233564788)
console.log(u1.phonenumber)    //undefined
console.log(u1.getphonenumber())     //15233564788 
u1.setphonenumber(12345678912)
console.log(u1.getphonenumber())     //12345678912